Photovoltaic panels are exposed to natural environments, and thus, their surfaces (light receiving surfaces) get dirty. Dirt leads to reduced power generation efficiency. In particular, with respect to a photovoltaic apparatus of a concentrator type which tracks the sun, there are cases where its power generation efficiency is greatly (about 20%, for example) reduced when the surface thereof gets dirty. For example, with respect to a photovoltaic apparatus installed in a desert district, when dust has accumulated on the surface thereof and become sticky due to dew condensation, such dust will not easily come off, which results in reduced power generation efficiency.
Thus, there has been proposed a photovoltaic apparatus provided with a surface cleaning function (for example, see FIG. 2 of PATENT LITERATURE 1, and FIG. 1 and FIG. 2 of PATENT LITERATURE 2).
Each prior art above has a configuration in which the cleaning is performed by a brush moving on the surface.